There exists a constant search to develop new olefin polymerization catalysts, catalyst activation processes, and methods of making and using catalysts. Mono-1-olefins (α-olefins), including ethylene, can be polymerized with catalyst compositions employing titanium, zirconium, vanadium, chromium or other metals, impregnated on a variety of support materials, often in the presence of cocatalysts. These catalyst compositions may be useful for both homopolymerization of ethylene, as well as copolymerization of ethylene with co-monomers such as propylene, 1-butene, 1-hexene, or other higher alpha-olefins.